Google DNS DEC 03 2009

Google announced their public DNS server today. I'm using it right now. There's been a bunch of speculation as to why Google is offering this service for free but the reason is pretty simple: they want to speed up people's Google search results. In 2006, Google VP Marissa Mayer told the audience at the Web 2.0 conference that slowing a user's search experience down even a fraction of a second results in fewer searches and less customer satisfaction.

Marissa ran an experiment where Google increased the number of search results to thirty. Traffic and revenue from Google searchers in the experimental group dropped by 20%.

Ouch. Why? Why, when users had asked for this, did they seem to hate it?

After a bit of looking, Marissa explained that they found an uncontrolled variable. The page with 10 results took .4 seconds to generate. The page with 30 results took .9 seconds.

Half a second delay caused a 20% drop in traffic. Half a second delay killed user satisfaction.

Former Amazon employee Greg Linden backs up Mayer's claim:

This conclusion may be surprising -- people notice a half second delay? -- but we had a similar experience at Amazon.com. In A/B tests, we tried delaying the page in increments of 100 milliseconds and found that even very small delays would result in substantial and costly drops in revenue.